The chi-square (Χ2) distribution table is a reference table that lists chi-square critical values. A chi-square critical value is a threshold for statistical significance for certain hypothesis tests and defines confidence intervals for certain parameters.
For each observed number in the table subtract the corresponding expected number (O — E). Square the difference (O —E)². Divide the squares obtained for each cell in the table by the expected number for that cell (O - E)² / E. Sum all the values for (O - E)² / E.
A chi-square test is a statistical test used to compare observed results with expected results. The purpose of this test is to determine if a difference between observed data and expected data is due to chance, or if it is due to a relationship between the variables you are studying.